The present invention relates to a telescoping tower formed of a plurality of nesting sections, including an inner section, an outer section, and generally one or more intermediate sections, with the inner and intermediate sections being slidable relative to an adjacent exterior section between a nested or retracted position, a deployed or locked position, and a release position. The tower of the present invention is especially suitable for use as part of a transportable broadcast antenna. Of particular importance to the present invention is a latch or locking mechanism which allows the tower sections to be locked and unlocked by an operator from ground level.
Various telescoping towers have been described in the prior art. For example, U.S. Pat. No. 3,361,456 to Durand describes a telescoping tower, such as a crane tower, having a locking system in which support arms on an inner tower section extend outwardly to rest on beating surfaces on an adjacent tower section when the tower is extended, and are pivoted away from the bearing surfaces to allow the tower to be lowered. The arms initially extend downward. When the tower is deployed, the arms are moved above the bearing surfaces, and are pivoted outward by contact with pins. The inner tower is then lowered so that the arms rest on the surfaces to hold the inner section in the extended position. When the tower is to be lowered, the inner section is further extended to contact the arms with pins, pivoting the arms downward, and allowing the inner section to be lowered without the arms contacting the beating surfaces.
U.S. Pat. No. 1,899,742 to Bay describes a locking mechanism for an extension ladder having a triangular inner section which telescopes from a triangular outer section. The mechanism comprises pivotal hooks which are cammed away from the ladder rung on their upward movement, and then engage a rung when lowered. To release the latch, the inner ladder section is extended further upward, to close fingers over the hooks, preventing their engagement with a rung on the downward movement.
U.S. Pat. No. 4,254,423 to Reinhard describes a locking mechanism for an antenna mast. The antenna is formed of a plurality of nested, telescoping sections which are deployed by hydraulic or pneumatic means. In the fully extended position, spring loaded lever arms extend into recesses to hold the section is a upright position. To release the locking mechanism, the operator pulls on a rope to pivot the lever arms out of the recesses by forcing a camming surface against the arms.
U.S. Pat. No. 4,483,109 to MacDonald et al describes an emergency latching system for a telescoping boom comprised of a pivotal latch plate which engages a slot in an adjacent inner section of the boom if the telescoping chain breaks.
U.S. Pat. No. 5,228,251 to Frigon describes a telescoping mast which may be used to support an antenna. The nested sections of the mast may be locked in an extended position with tabs which are bent inwardly to engage the bottom of the adjacent inner section. To retract a mast section, the inner section is raised and the tab is bent outwardly to remove it from the path of the inner section.
U.S. Pat. No. 3,284,972 to Werner describes a telescoping antenna tower comprised of a plurality of nesting triangular sections. The Werner tower is assembled horizontally while on the ground and then raised into position. Sections are held in the extended position by locking pins.
U.S. Pat. No. 4,932,176 to Roberts et al describes a transportable, telescoping antenna carried on the back of a track. The antenna is pivoted from a horizontal position to a vertical position by hydraulic means. The antenna sections are extended by a cable extending around a series of pulleys, with the cable being pulled by a winch, and are held in the extended position by cable tension.
U.S. Pat. No. 5,101,215 to Creaser describes a telescoping tower comprised of a plurality of nesting triangular sections that are extended by retracting a single cable running from the top of each section to the bottom of the adjacent inner section, and then up to the top of that section.
U.S. Pat. No. 4,871,138 to Sauter describes a telescoping tower in which each inner section is locked in the extended position by a latching mechanism including a locking pin which is cammed into a slot in the adjacent outer section, and withdrawn when the tower is lowered.
U.S. Pat. No. 5,163,650 to Adams et al describes a latching mechanism involving the use of a rotatable disk which is rotated into locking position beneath a bar on the adjacent inner section to lock the sections in an extended position, and then rotated to unlock the sections.
While the above and other telescoping towers are described in the prior art, there is still a need for a tower comprised of telescoping sections which can be securely latched in the deployed position, and then released from ground level by the operator. A latching mechanism which will support high loads and levels of stress is also desired, as is a latching mechanism which will provide a greater contact area between tower sections, and thus improved conductivity, when the tower is used as a broadcast antenna.